sea anemone

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sea anemone

(ənĕm`ənē'), any of the relatively large, predominantly solitary polyps (see polyp and medusapolyp and medusa,
names for the two body forms, one nonmotile and one typically free swimming, found in the aquatic invertebrate phylum Cnidaria (the coelenterates). Some animals of this group are always polyps, some are always medusae, and some exhibit both a polyp and a medusa
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) of the class Anthozoa, phylum Cnidaria. Unlike the closely related corals, these organisms do not have a skeleton. Sea anemones occur everywhere in the oceans, at all depths, but are particularly abundant in coastal waters. Many are beautifully colored (reds, pinks, yellows) and look like flowers when the oral, or feeding, end, equipped with many extensions called tentacles, is fully open. Some anemones are tiny, but most are from one to several inches (2.5–10 cm) long; the genus Stoichactis in the Great Barrier Reef off the coast of Australia may reach 3 ft (90 cm) in diameter at the expanded oral end. Most sea anemones attach temporarily to submerged objects; a few thrust themselves into the sand or live in furrows; a few are parasitic on other marine organisms. Some anemones feed on small particles, which are caught with the aid of a mucus secretion and moving currents that are set up by the tentacles. Most sea anemones are predaceous, immobilizing their prey with the aid of specialized stinging cells called nematocysts. Metridium is the genus most often studied in classrooms. The burrowing anemone, Cerianthuss, occurs on both Pacific and Atlantic coasts; some may reach nearly 2 ft (60 cm) in length. Sea anemones are classified in the phylum CnidariaCnidaria
or Coelenterata
, phylum of invertebrate animals comprising the sea anemones, corals, jellyfish, and hydroids. Cnidarians are radially symmetrical (see symmetry, biological).
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, class Anthozoa, subclass Zoantharia.

sea anemone

[′sē ə‚nem·ə·nē]
(invertebrate zoology)
Any of the 1000 marine cnidarians that constitute the order Actiniaria; the adult is a cylindrical polyp or hydroid stage with the free end bearing tentacles that surround the mouth.

sea anemone

any of various anthozoan coelenterates, esp of the order Actiniaria, having a polypoid body with oral rings of tentacles